Litter Soil Layers Research Articles

Litter Decomposition in Retreating Coastal Forests

AbstractRising sea levels lead to the migration of salt marshes into coastal forests, thereby shifting both ecosystem composition and function. In this study, we investigate leaf litter decomposition, a critical component of forest carbon cycling, across the marsh-forest boundary with a focus on the potential influence of environmental gradients (i.e., temperature, light, moisture, salinity, and oxygen) on decomposition rates. To examine litter decomposition across these potentially competing co-occurring environmental gradients, we deployed litterbags within distinct forest health communities along the marsh-forest continuum and monitored decomposition rates over 6 months. Our results revealed that while the burial depth of litter enhanced decomposition within any individual forest zone by approximately 60% (decay rate = 0.272 ± 0.029 yr−1 (surface), 0.450 ± 0.039 yr−1 (buried)), we observed limited changes in decomposition rates across the marsh-forest boundary with only slightly enhanced decomposition in mid-forest soils that are being newly impacted by saltwater intrusion and shrub encroachment. The absence of linear changes in decomposition rates indicates non-linear interactions between the observed environmental gradients that maintain a consistent net rate of decomposition across the marsh-forest boundary. However, despite similar decomposition rates across the boundary, the accumulated soil litter layer disappears because leaf litter influx decreases from the absence of mature trees. Our finding that environmental gradients counteract expected decomposition trends could inform carbon-climate model projections and may be indicative of decomposition dynamics present in other transitioning ecosystem boundaries.

Composition of the soil fauna community and leaf litter stock in agro-forestry systems and secondary forestry

Agro-Forestry Systems (AFS), in addition to being a means of providing income, can be considered an alternative way of helping conserve biodiversity, both above and below ground. The aim of this study was to evaluate the accumulation of tree leaf litter and its nutrient content as well as the composition of fauna in the soil-litter layer in two Agro-Forestry Systems (AFS-1 and AFS-2), using as reference an area of secondary Forest (SF), in the Quilombola do Campinho da Independência community, Paraty, in the state of Rio de Janeiro (RJ), Brazil. The collection of accumulated leaf litter and soil-litter fauna was carried out from four sample points in each area and at two different seasons of the year, the rainy and the dry season. The leaf litter stock and its nutrient content (Ca, Mg, P, K and N) were measured. The extraction of fauna was carried out according to Tüllgren’s method, modifying the Berlese funnel. The stock of accumulated leaf litter differed between the two areas only in the rainy season; the amounts were smaller in AFS-2. In general, the Agro-Forestry Systems were very similar to the secondary forest in terms of levels and/or stock of nutrients in the majority of cases, at least in one of the seasons studied. The composition of the soil fauna groups in the Agro-Forestry System (AFS-1 and AFS-2) had a high degree of similarity to that found in the forest, and these systems mainly favour the populations of groups like Collembola and Formicidae.

A New Passive Microwave Tool for Operational Forest Fires Detection: A Case Study of Siberia in 2019

The purpose of this paper is to present a new method for early detection of forest fires, especially in forest zones prone to fires using microwave remote sensing and information-modeling tools. A decision-making system is developed as a tool for operational coupled analysis of modeling results and remote sensing data. The main operating structure of this system has blocks that calculate the moisture of forest canopy, the soil-litter layer, and the forest physical temperature using the observed brightness temperature provided by the flying platform IL-18 equipped with passive microwave radiometers of 1.43, 13.3 and 37.5 GHz frequencies. The hydrological parameters of the forest are assessed with both a developed regional hydrological model and remote sensing observations. The hydrological model allows for the detection of fire-prone zones that are subject to remote sensing when modeling results are corrected and thermal temperatures are evaluated. An approach for the real time forest fires classification via daytime remote sensing observations is proposed. The relative theoretical and experimental results presented here have allowed us to use a new approach to forests monitoring during periods of potential fire. A decision-making algorithm is presented that aims at analyzing data flows from radiometers located on the remote sensing platform to calculate the probability of forest fire occurring in geographical pixels. As case study, the state of forest fires that occurred in Siberia in 2019 using microwave remote sensing measurements conducted by a flying IL-18 laboratory is presented. This remote sensing platform is equipped with optical and microwave tools that allow the optical and microwave images of the observed forest areas. The main operating frequencies of microwave radiometers are 1.43, 13.3 and 37.5 GHz. Microwave radiometers provide data on water content in the forest canopy and on litter and physical temperatures. Based on the long-term measurements made in Siberia, the possible improvement of the proposed decision-making system for future relevant studies is discussed in detail. The basic idea of cost-effective monitoring of forested areas consists of a two-stage exploration of fire risk zones. The first monitoring stage is performed using the hydrological model of the study area to identify low moisture areas of the forest canopy and litter. The second stage of monitoring is conducted using the remote sensing platform only in the local fire-dangerous areas in order to more precisely identify the areas prone to fire and to detect and diagnose real burning zones. The developed algorithm allows the calculation of physical temperatures and the detection of temperature anomalies based on measured brightness temperatures. Finally, the spatial distribution of the probability of forest fire occurrence is given as an example of the decision-making system along with a comparison of this distribution with the satellite images provided by the EOSDIS Land data.

Snow microhabitats provide food resources for winter-active Collembola

The feeding ecology of soil animals is seldom investigated in the winter when the soil is covered with a layer of snow. Collembola (springtails) are winter-active arthropods that appear on the snow surface, especially on sunny days, and remain active in microhabitats under the snow. Since winter-active Collembola must be consuming food, we assessed the food resources for these Collembola with stable isotope and bacterial 16S rRNA gene amplicon sequencing methods. We collected two Desoria species from the snow surface and Tomocerus cf. jilinensis from subnivean microhabitats. The stable isotope signatures of winter-active Collembola species differed significantly from the soil litter layer. The isotopic signature of Desoria sp.1 was similar to the snow. Furthermore, the putative food resource (bacteria) ingested by Desoria sp.3 and Tomocerus cf. jilinensis were more from snow than from litter. All three Collembola species ingested a large proportion of Cyanobacteria. Moreover, a large proportion of bacteria associated with Collembola were putative symbionts. Bacterial communities and their associated metabolic functions were more similar in the two congeneric Desoria species than with Tomocerus cf. jilinensis. Our findings suggest that winter-active Collembola mainly feed on resources present in the snow layer. Stable isotope and amplicon sequencing methods are promising techniques to evaluate the diets of soil animals that remain active in snow-covered soils.

Fluorescence Characteristics of Dissolved Organic Matter (DOM) in Percolation Water and Lateral Seepage Affected by Soil Solution (S-S) in a Lysimeter Test.

The composition and structure of dissolved organic matter (DOM) are sensitive indicators that guide the water infiltration process in soil. The DOM chemical composition in seepage affects river water quality and changes soil organic matter (SOM). In this lysimeter test study, fluorescence spectra and optical indices were used to examine the interaction between the percolation water (P-W) and leachate water (L-W) DOMs affected by the soil solution (S-S). The L-W DOM had a higher aromaticity (SUVA254), average molecular weight (S275-295) and terrestrial source (fluorescence index (FI)), but fewer autochthonous sources (biological index (BIX)) than the P-W DOM. Organic carbon standardization (OCS) and protein- (PLF), fulvic- (FLF) and humic-like fluorescence (HLF) intensity showed that L-W DOM increased 44%, 55% and 81%, respectively, compared to the P-W DOM. The linear regression slopes between OCS FLF and PLF were 0.62, 1.74 and 1.79 for P-W, L-W and S-S, respectively. The slopes between OCS HLF and PLF were 0.15, 0.58 and 0.64 for P-W, L-W and S-S, respectively. The P-W DOM was in contact with the soil litter layer, where S-S labile lignin phenolic compounds released and dissolved into the L-W DOM. This increased its aromaticity, and extent of humification.

Positive relationship between species richness and aboveground biomass in Kumaun Himalayan forest

Understory vegetation is an important part of forest ecosystem which affect the physical and chemical properties of soil, quality and quantity of forest litter and water storage capacity of litter soil layer. Thus, the influence of soil nutrients on the understory species composition of forest ecosystem cannot be ignored. The authors set 15 typical plots with area of 1 × 1 m in chir pine (Pinus roxburghii Sarg.), oak (Quercus leucotrichophora A. Camus)—chir pine mixed and oak–cypress (Cupressus torulosa D. Don) mixed forest. Chemical properties of the soil were analyzed at 0–10 cm, 10–20 cm and 20–30 cm in all the selected forest types. Phytosociological and diversity parameters were also calculated for each forest type. The present study reveals that carbon, nitrogen, pH and phosphorus are the most important environmental drivers which influence understory species composition. Plant species richness significantly correlated with species composition. To maintain the diversity and structure of ecosystems we should consider the co-evolution of both vegetation and soil. Further studies on climate and microorganism are needed to further explore the interactive relationships among vegetation and soil properties.

The biodiversity and community structure of soil ciliates of Talish forests in south-eastern Azerbaijan

New information on the fauna of the soil ciliates of south-eastern Azerbaijan is presented in this article. As a result of surveys conducted in 2017–2019, 65 species of soil ciliates assigned to 33 families were recorded. The highest diversity of pedobiont ciliates was observed in Masalli and Lankaran forest soils. On the other hand, the lowest species diversity was recorded in the Astara region. The highest species diversity was found for the family Colpodidae, of which 7 species were found. Four of them belong to the pedobiont genus Colpoda. Almost all representatives of this genus are typically soil species and euribionts with wide ecological plasticity. In addition, two species that are the representatives of the genus Tillina were found in soil, but they can be occasionally found in freshwater bodies. It should be noted that the special climatic conditions of south-eastern Azerbaijan impact on the distribution regularity of ciliates in the mountain-forest soils. The accumulation of ciliates in forest soils in spring was observed in the upper horizon of the 5 cm soil litter layer in summer. Due to the decrease in humidity in upper layers, pedobiont ciliate migrates to deeper layers (10–15 cm), and in autumn with the increase in precipitation and humidity in the upper soil horizons, the mass of soil ciliates is again localized in the forest litter and in the upper soil layer. It is also worth noting another specific complex of ciliates in the forest soils of south-eastern Azerbaijan. In early spring and autumn, with the maximum moisture content in the forest soil, we often observed ciliates, which usually dwell in fresh waters. Among them are representatives of such genera as Zosterodasys, Nassula, Aspidisca, Blepharisma, Frontonia, Urotricha etc. The species diversity and community similarity index of soil ciliates in Talish forests of Lankaran natural area were also calculated. The study attempts to compare the difference in ciliates community among five different regions of south-eastern Azerbaijan. The analysis showed that there are 3 clusters of the similarity of species diversity of ciliate communities. The similarity between the ciliate fauna of the high mountainous regions and fauna of the plain regions was 52.15–69.00 %.

CЕЗОННА ДИНАМІКА ФРАКЦІЙНОГО СКЛАДУ ЛІСОВОЇ ПІДСТИЛКИ НПП "ГОЛОСІЇВСЬКИЙ"

Leaf litter is an important structurally fucnctional element of forest ecosystem, dynamic processes in which create a connection between phytocenosis and edaphotope. Accumulation of litter material and its decomposition rate characterize intensity of substance circulation in forest ecosystem. The present article deals with the results researching of the peculiarities of the forming and decomposition of soil litter layer in the hornbeam oak in the conditions of Holosiivskyi National Nature Park (Kyiv) were examined. Its considerable sizes on the north slope of ravine coast system (16,4 t/ha in autumn, 4,3 t/ha in the summer) were determed. Analysis of litter supply at the end of abscission showed a lack of significant differences in different sections of the terrain (12,3–16,4 t/ha). During the winter period, litter volumes are significantly reduced due to intensive mineralization processes under the snow cover. Most intensively, these processes take place in areas of the slope. Fractional composition of the litter did not generally depend on the location of the experimental area by relief elements. A dominating faction in autumn and spring was fall (65–69 % of the total mass). In the summer, a portion of dust (38-46 %) increased. The smallest number of branches was observed in autumn and winter, their scope was between 11-22 % in all research areas. The maximum amount of branches was observed at all areas in the summer. Their volume was 27-49 %. The scope of seeds and its residues was insignificant and amounted to 1-3 % during the year. The speed of mineralization of cellulose by an application method with the use of filter paper is determined. The rate of decomposition of cellulose in the conditions of the southern and northern ravine slope turned out to be similar to the maximum in March and July-August.

三峡库区马尾松林土壤-凋落物层酶活性对凋落物分解的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡库区马尾松林土壤-凋落物层酶活性对凋落物分解的影响 DOI: 10.5846/stxb201305261185 作者: 作者单位: 中国林业科学研究院亚热带林业研究所,中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院亚热带林业研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 林业公益性行业科研专项（201104008）；“十二五”科技支撑资助项目（2011BAD38B04） Effect of soil-litter layer enzyme activities on litter decomposition in Pinus massoniana plantation in Three Gorges Reservoir Area Author: Affiliation: Research Institute of Subtropical Forestry,Chinese Academy of Forestry,Fuyang,Zhejiang,Key Laboratory of Forest Ecology and Environment,the State Forestry Administration,Key Laboratory of Forest Ecology and Environment,the State Forestry Administration,Key Laboratory of Forest Ecology and Environment,the State Forestry Administration,Research Institute of Subtropical Forestry,Chinese Academy of Forestry,Fuyang,Zhejiang Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:凋落物的彻底降解是在凋落物和土壤酶系统的综合作用下完成，酶活性的提高有利于凋落物-土壤有机物质的分解和养分释放。通过对三峡库区30年生马尾松林凋落物分解、凋落物-土壤层酶活性季节动态及其对分解的影响进行研究，结果表明：30年生马尾松林凋落物经过540 d的分解后干重剩余率是59.80%；凋落物层酶活性季节动态明显，氧化还原酶活性均是11月最低，3月最高；土壤过氧化物酶活性季节变化显著且均是11月最低，多酚氧化酶活性9月较高，而过氧化物酶活性则是6月较高。马尾松林凋落物层酶活性与土壤层酶活性差异较大，且水解酶活性差异较氧化还原酶活性差异大，凋落物层脲酶活性、纤维素酶活性和蔗糖酶活性11月、6月、9月分别是0-5 cm土壤层的6.33倍、3.24倍、10.29倍，68.14倍、16.16倍、24.81倍，25.07倍、31.88倍、29.20倍。凋落物分解速率均与土壤、凋落物层氧化还原酶活性呈极显著“S”形曲线，与凋落物层水解酶活性呈二次函数关系，与土壤层水解酶均呈极显著的线性关系。凋落物质量能引起凋落物-土壤层酶活性变化，酶活性的改变反过来影响凋落物的分解，因此，凋落物-土壤层酶活性差异与凋落物分解阶段和对共同影响因素（凋落物质量、土壤温度、水分含量和土壤养分等）的敏感性不同有关，凋落物-土壤层酶的相互作用共同影响森林生态系统的物质循环和养分循环过程。 Abstract:The complete degradation of litter results from the combined enzyme activities in litter layer and soil layer, and their improvement is helpful to organic matter decomposition and nutrient release. Litter decomposition and the seasonal dynamic of soil-litter layer enzyme activities were studied on 30-year-old P. massoniana forest in Three Gorges Reservoir Area. The results showed that the remaining mass was 59.80% after 540 days decomposition. The decomposition rate was relatively fast during the decomposition 0-180 d, and relatively slow during 180-270 d. The period of 50% mass loss and 95% mass loss was 2.11 a and 9.15 a, respectively. The litter layer enzyme activities exhibited a remarkable seasonal dynamics, with the lowest enzyme activity occurring in November and the highest in March for oxidoreductase activity. Polyphenoloxidase activity and peroxidase activity of litter layer in March were 4.60 times and 6.07 times as high as those in November, respectively, while the dynamic of hydrolase activity in litter layer was irregular variation. The seasonal dynamics of soil layer peroxidase activity was remarkable with the lowest value occurring in November, and the highest in June. Polyphenoloxidase activity was the highest in September. The seasonal dynamics of soil layer hydrolase activity was irregular variation, the seasonal dynamical of soil urease activity was not significant (P>0.05), while the cellulose activity and sucrase activity was significant (P<0.05) with the sequence of September < June < November for sucrase activity, and the sequence of November < September < June for cellulose activity. Soil enzyme activity in the vertical direction was decreased gradually with soil depth except peroxidase activity. There was a notable difference in enzyme activity between litter layer and soil layer, and the difference in hydrolase activity was greater than in oxidoreductase activity. Litter layer urease activity, cellulase activity and sucrase activity were 6.33 times, 3.24 times, 10.29 times as high as those in 0-5 cm soil layer in November; 68.14 times, 16.16 times, 24.81 times in June, and 25.07 times, 31.88 times, 29.20 times in September, respectively. Litter polyphenoloxidase activity in November, June and September were 1.76 times, 1.45 times and 2.07 times as high as those in 0-5 cm soil layer, and the corresponding value were 0.40 times, 0.64 times and 0.56 times for peroxidase activity, respectively. There was a close relationship between litter-soil enzyme activities. Litter decomposition rate was significantly correlated in S-shaped curve with oxidereductase activity both in litter and soil layer, probably because oxidoreductase activity dynamic is complex and influenced by soil pH value, nutrient content, soil layer distribution and so on. There were significant quadratic function (P<0.01) between litter decomposition rate and hydrolase activity in litter layer, while litter decomposition rate was significantly linearly related (P<0.01) to the hydrolase in soil layer. Litter quality could change the enzyme activity in litter and soil layer, in return, enzyme activity could affect litter decomposition rate. Therefore, the difference of enzyme activity between litter and soil layer is related with litter decomposition stage and the different sensitivity of the common impact factors including litter quality, soil temperature, water content and soil nutrients. The interactions of litter-soil layer enzyme activity influence material circulation and nutrient cycling process of forest ecosystem. 参考文献 相似文献 引证文献

광주천 고수부지에 조성한 자유수면인공습지의 인 제거

하천수를 정화하는 자유수면인공습지의 정수식물 성장기(4~9월)와 비성장기(1~3월과 10~12월)의 <TEX>$PO_4-P$</TEX>와 TP제거율을 비교 연구하였다. 실험 습지 시스템은 광주광역시를 흐르는 광주천 중류 고수부지에 2008년 조성되었으며, 길이 46m, 폭 5m 규모이다. 2008년 포트에서 2년 자란 부들(Typha angustifloria L.)과 줄(Zizania latifolia Turcz)을 시스템의 1/2씩 각각 식재하였다. 광주천의 물이 자연유하로 시스템에 유입되며, 처리수는 광주천으로 방류된다. 유입수의 양과 수심은 밸브와 위어(weir)로 조절할 수 있다. 유입수 및 유출수의 인 농도를 2010년 1월부터 12월까지 7~10일 간격으로 조사 분석하였다. 하루에 약 <TEX>$710m^3$</TEX>의 하천수가 시스템으로 유입되어, 체류시간은 약 1.5hr이었다. 조사기간 유입수와 유출수의 <TEX>$PO_4-P$</TEX> 평균농도는 각각 0.144, 0.105mg/L이었으며, <TEX>$PO_4-P$</TEX> 평균제거율은 28.1%였다. 유입수와 유출수의 TP평균농도는 각각 0.144, 0.105mg/L이었으며, TP 평균제거율은 20.7%를 보였다. t 검정결과, 정수식물 성장기의 <TEX>$PO_4-P$</TEX> 제거율(31.448)이 비성장기 <TEX>$PO_4-P$</TEX> 제거율(25.829)보다 높았으며(p<0.001), 정수식물 성장기의 TP 제거율(27.230)도 비성장기의 TP 제거율(14.856)보다 높게(p<0.001) 나타났다. 인공습지에서 인 제거는 잔재물-토양 층의 흡착, 입자성 인과 Ca, Fe, Al과 결합된 인산염의 침전, 그리고 정수식물의 흡수가 중요하다. 정수식물 성장기가 비성장기보다 <TEX>$PO_4-P$</TEX>와 TP의 제거율이 상대적으로 높은 원인은 흡착과 침전에 의한 인 제거는 계절에 관계없이 일어나나, 정수식물의 흡수는 성수식물 성장기에만 일어나기 때문이다. Removal rates of <TEX>$PO_4-P$</TEX> and TP in a free water surface wetland system were investigated. The system was established in 2008 on a floodplain in the middle reach of the Gwangju Stream flowing through Gwangju City. Its dimensions were 46 meters in length and 5 meters in width. Two year old Typha angustifloria L. growing in pots were planted on half of the area and Zizania latifolia Turcz on the other half in 2008. Stream water was funneled into the wetlands by gravity flow, and its effluent was discharged back into the stream. The influent volume was controlled by valves and water depth was adjusted by wires. Volume and water quality of inflow and outflow were analyzed from January to December in 2010. Inflow into the system averaged approximately <TEX>$710m^3/day$</TEX> and hydraulic residence time was about 1.5 hours. Average influent and effluent <TEX>$PO_4-P$</TEX> concentration were 0.144 and 0.103mg/L, respectively, and <TEX>$PO_4-P$</TEX> abatement amounted to 28.6%. Influent and effluent TP concentration averaged 0.333 and 0.262mg/L, respectively, and TP retention reached to 20.7%.<TEX>$PO_4-P$</TEX> removal rate(%) during plant growing season(31.448) was significantly high(p<0.001) when compared with that during plant non-growing season(25.829). TP abatement rate(%) during plant growing season(27.230) was also significantly high(p<0.001) when compared with that of the non-growing season(14.856). Major phosphorous removals in the system resulted from adsorption of phosphorous in the litter-soil layers; sedimentation of particulate phosphorous and Ca, Al, Fe bounded phosphates; and absorption of phosphorous by emergent plants. The adsorption and sedimentation occurred throughout the year, however, the absorption took place during plant growing season. This resulted in higher removals of <TEX>$PO_4-P$</TEX> and TP during plant growing season.

Scientific Opinion on the importance of the soil litter layer in agricultural areas

Scientific Opinion on the importance of the soil litter layer in agricultural areas

Soil mesofauna of taiga burozems

In the burozems of the plains, the composition of the invertebrates and saprophages (the prevailing primary destroyers) differed from that in the mountainous soils only by the absence of millipedes of the Geophilomorpha order. At the same time, the differences in these characteristics between the burozems and soddypodzolic soils of the neighboring coniferous-broad-leaved forests were more significant: in the latter, the composition of the ecological groups of earthworms was more diverse. Among the earthworms, secondary destroyers (detritophages) consuming well-decomposed residues of plants and animals predominated: Aporrectodea caliginosa, A. rosea, and Octolasium lacteum. In the taiga burozems, among the secondary destroyers, very few O. lacteum among the earthworms, and Polyzonium germanicum among the millipede diplopods were found. Primary destroyers that only comminute plant tissues (Dendrobaena octaedra and Dendrodrilus rubidus f. tenuis) were the main representatives in the invertebrate population of these soils. The differences also concerned the group composition and the proportion between the life forms of the earthworms. In the southern taiga burozems, only the litter (Dendrobaena octaedra and Dendrodrilus rubidus f. tenuis) earthworms and species of the upper soil layer (Octolasium lacteum) were present. In the mountainous burozems of the Transcarpathian region, litter inhabitants (Dendrobaena attemsi and Aporrectodea submontana), soil-litter inhabitants (Dendrobaena alpina—Transcarpathian region), and inhabitants of the upper (Helodrilus cernosvitovianus) and middle (Aporrectodea carpathica and A. sturanyi) soil layers (in the Primorskii region, only the soil-litter Eisenia nordenskioldi) were identified. In the soddy-podzolic soils, dwellers of the middle soil layers (Aporrectodea caliginosa, A. rosea, and Lumbricus terrestris) were constantly present along with the species dwelling in the litter and in the upper soil layers (in the litter—Dendrobaena octaedra, Dendrodrilus rubidus f. tenuis, and L. castaneus; in the litter-soil layer—L. rubellus; in the upper soil layer—Octolasium lacteum). The higher diversity of the earthworm life forms in the soddy-podzolic soils points to the stronger development of their humus horizons as compared to those horizons in the burozems of the southern taiga and mountains.

Photostimulation of Hypocrea atroviridis growth occurs due to a cross-talk of carbon metabolism, blue light receptors and response to oxidative stress

Light is a fundamental abiotic factor which stimulates growth and development of the majority of living organisms. In soil saprotrophic fungi, light is primarily known to influence morphogenesis, particularly sexual and asexual spore formation. Here we present a new function of light, the enhancement of mycelial growth. The photostimulated mycelial growth of the soil fungus Hypocrea atroviridis was detected on 17 (out of 95 tested carbon sources) carbohydrates and polyols, which are metabolically related to cellulose and hemicelluloses, and which are mainly available in the upper soil litter layer. This stimulation depends differently on the function of the two blue light receptor proteins BLR-1 and BLR-2, respectively, BLR-1 being responsible for carbon source selectivity and response to permanent light. Evocation of oxidative stress response in darkness imitates the photostimulation on nine of these carbon sources, and this effect was fully dependent on the function of BLR-1. We conclude that light in combination with the availability of litter-specific carbon sources serves as a signal for the fungus to be above ground, thereby stimulating fast growth in order to produce a maximum of propagules in the shortest time. We further deduce that this process involves oxidative stress response and the two blue light receptor proteins BLR-1 and BLR-2, the former playing the major role.

Earthworm abundance related to soil physicochemical and microbial properties in Accra, Ghana

The introduction of vermicomposting as a cost effective method of managing organic waste in Ghana depends on the suitability of local earthworms. At nine locations across Accra, the capital of Ghana, the soil-litter layer was sampled to evaluate the occurrence and abundance of surface dwelling earthworms (0 - 10 cm depth) and to investigate the relationship between earthworm abundance and soil properties (physicochemical and microbial). Eudrilus eugeniae (Kinberg), a rapidly growing large worm (adults reach 14 cm long), was the only earthworm collected from seven of the nine locations. Small unpigmented holonephric worms were collected at the other two locations. Earthworm densities ranged between 35 and 2175 individuals m -2 . Significant (P< 0.05) negative correlations existed between earthworm abundance and organic C and exchangeable Na. All locations tested positive for the microbial indicators; Total coliforms, Escherichia coli, Staphylococcus, Yeast and Moulds and Aspergillus. There was a significant (P< 0.01) positive correlation between earthworm abundance and all the bacterial indicators tested. Earthworm abundance was also weakly correlated (P < 0.1) with the yeast and mould loads.

Changes in density of nematodes, protozoa and total coliforms after transit through the gut of four epigeic earthworms (Oligochaeta)

Epigeic earthworms are detritivorous organisms that live and feed in the soil litter layer. These earthworms exert important effects on the presence of decomposer micro-organisms and their microbial grazers, which lead to changes in the rate of decomposition of the organic matter. To assess the effect of the transit through the gut of epigeic earthworms on the decomposer organisms, we analysed the gut contents of four epigeic species reared under laboratory conditions, with pig slurry as food source. The numbers of nematodes, protozoa (flagellates, testate and naked amoebae) and total coliforms in the hindgut of the earthworm species, Eisenia fetida, Eisenia andrei, Lumbricus rubellus and Eudrilus eugeniae, were compared with the numbers of the same organisms in the pig slurry. No nematodes were found after transit through the gut of the earthworms and there was a decrease between 85% and 98% in the numbers of total coliforms of the pig slurry (723 ± 125 × 10 3 CFU g −1 dw). The effect on the numbers of protozoa depended on both groups of protozoa and species of earthworm considered. The numbers of flagellates were greater in the gut samples of E. fetida and E. andrei (363 ± 46 × 10 3 MPN g −1 dw) than in the ones of L. rubellus and E. eugeniae (105 ± 26 × 10 3 MPN g −1 dw). The density of testate amoebae was not affected by the transit through the gut of earthworms, and the numbers of naked amoebae were greater in the gut samples of L. rubellus (2500 ± 780 × 10 3 MPN g −1 dw) than in the fresh pig slurry (755 ± 311 × 10 3 MPN g −1 dw). The results indicate that short-time effects associated with the digestive activity in the earthworm gut play an important role in the changes that epigeic species exert on the decomposer community.

New species of dictyostelid cellular slime moulds from Australia

During the 2001–2006 field seasons, samples for isolation of dictyostelid cellular slime moulds were collected at several localities in Queensland, the Northern Territory, Western Australia and Victoria. The majority of these samples were collected from the soil–litter layer on the ground, but some additional samples were obtained from the layer of organic matter (‘canopy soil’) associated with the bases of vascular epiphytes on the trunks and branches of trees in the tropical forests of northern Queensland. Many of the forms recovered from these samples could be assigned to described taxa, including such cosmopolitan species as Dictyostelium mucoroides, Polysphondylium pallidum, P. violaceum and D. giganteum. However, several others appear to represent new species, and eight of these (D. boomeransporum, D. flexuosum, D. granulosum, D. myxobasis, D. radiculatum, D. rotatum, P. australicum and P. stolonicoideum) are described herein. The large number of apparently undescribed forms suggests that the dictyostelid biota of Australia is relatively distinct when compared with that of any other continent.

Diversidad de ácaros (Acari: Prostigmata, Mesotigmata, Astigmata) asociados a la hojarasca de formaciones vegetales del Parque Universitario de la UCLA, Venezuela

Se estudió la diversidad de los ácaros (Prostigmata, Mesostigmata y Astigmata) habitantes del estrato suelo-hojarasca de un Matorral y un Bosque Deciduo del Parque Universitario de la UCLA (Universidad Centroccidental Lisandro Alvarado), Estado Lara, Venezuela, desde diciembre 2000 a noviembre 2001. El muestreo se realizó usando trampas de caída colocadas a lo largo de una transecta de 1.800 m en ambas localidades. Todos los morfotipos fueron montados en láminas microscópicas usando líquido de Hoyer. Se registró un total de 51 morfotipos de ácaros con predominancia del número de individuos pertenecientes a Prostigmata (2528) respecto a Mesostigmata (926) y Astigmata (12). En ambas localidades, Eupodidae (Prostigmata) y Macrochelidae (Mesotigmata) fueron las familias más abundantes. Se determinó mayor riqueza (S= 43), diversidad (H'= 2,67) y uniformidad (E= 0,69) de morfotipos en el Bosque Deciduo al ser comparado con los valores obtenidos en el Matorral (S= 36, H'= 2,12 y E= 0,52). Ambas zonas mostraron un índice de similitud (J') de 0,59. La pendiente de la curva de diversidad-dominancia permitió inferir que el Matorral constituye un hábitat más disturbado que el Bosque Deciduo a pesar de albergar mayor número de individuos. Se requiere realizar estudios más detallados que sirvan de base para determinar el rol de la acarofauna en el equilibrio de la red trófica de suelo de las regiones tropicales.

Variation in reproductive characteristics of Eupatorium adenophorum populations in different habitats

SummaryThe invasive plant, Eupatorium adenophorum, produces large numbers of small seeds with a high germination rate. However, this investigation showed that E. adenophorum populations in an evergreen broad‐leaved forest had a high proportion of seedlings when compared with clonal plants. Whereas an opposite pattern was found in a deciduous broad‐leaved forest and in a roadside site. A seed addition experiment where E. adenophorum seeds were added to each of the three habitats did not increase the number of E. adenophorum seedlings at any of the three field sites. Field and greenhouse experiments demonstrated that a soil litter layer significantly reduced the number of E. adenophorum seedlings during the early seedling emergence period. However, at later periods, the litter cover did not affect survival and growth of individuals. The emergence of E. adenophorum seedlings was significantly increased in field experiments when there was no litter, and parental plants were removed. Finally, the growth of seedlings was significantly reduced when planted with their parental plants in a root box experiment. In the low‐resource environment of the evergreen broad‐leaved forest, E. adenophorum reproduced primarily by its abundant seed production. In the more open deciduous broad‐leaved forest and roadside site, the populations reproduce primarily by vegetative clones that can grow quickly, are better competitors and could take advantage of the high‐resource environment.

Fertilizing and liming in a heather area of Norway

In a 6 years’ field experiment in a podzolized heather area in Norway the effects of liming and P and Cu fertilization were tested versus changes in vegetation and soil chemistry. The vegetation altered slowly, particularly the woody species, but pronounced over years. Liming had a positive effect on all species except Deschampsia flexuosa and Vaccinium myrtillus, P tended to favour all except V. myrtillus, and Cu promoted all except Nardus stricta, V. oliginosum and V. myrtillus. Surface spreading of liming material and fertilizers caused distinct lime, phosphorus and copper effects and interactions in the soil litter layer. Liming markedly increased pH and Ca level and stimulated microbial activity, whilst the fertilizers increased P and Cu availability in soil. Cu fertilization counteracted a feared Cu deficiency when liming marginal soils. Gradually the changes penetrated into deeper soil layers. This strong chemical influence led the podzol into a cambisol cycle, characterized by retention of humus in the E layer, accompanied by a slight increase in pH, elevated levels of Kjeldahl-N, AL dissolved and exchangeable Ca, and in CEC and BS.

The mobility of anthropogenic129I in a shallow sand aquifer at Sturgeon Falls, Ontario, Canada

SummaryThe transport and partitioning of129I has been examined for a shallow groundwater flow system at Sturgeon Falls in northeastern Ontario. Recharge into a sandy surficial postglacial deltaic aquifer occurs in the vicinity of a seasonally-wet boreal forest. Concentrations of stable iodine,129I, tritium, radiocarbon, stable isotopes and major ions were measured on samples of groundwater and precipitation. The present-day tritium profile delineates the position of the early 1960's above-ground nuclear weapons pulse at a depth of approximately 12 m.The concentrations of stable iodine for groundwaters above, near and below the above-ground nuclear weapons pulse range from 0.07 to 1.7 ppb. Over that same interval129I concentrations decreased from 1.9 × 106atoms/L at 9 m, to approximately 1.9 × 105atoms/L in tritium-depleted waters at 35 m, below the present-day depth of the recharging above-ground nuclear weapons peak at approximately 12.7 m. No substantial increases in the levels of129I were evident in waters sampled near the location of the above-ground nuclear weapons peak.The129I values in the lower aquifer are 1 to 2 orders of magnitude greater than published estimates of pre-bomb129I (103to 104atoms/L), and indicate contribution of129I from the fissiogenic decay of238U in the basal granite bedrock or from leaching of129I from the aquifer grains.A precipitation sample collected at Sturgeon Falls had concentrations of stable iodine and129I of 0.2 ppb and 8.5 × 107atoms/L, respectively. Concentrations of129I in Sturgeon Falls groundwaters are lower than those reported in other studies in central Canada, suggesting that the levels of129I in these groundwaters may have been attenuated by complexation or ion exchange with organic materials in the near-surface soil horizons. Such processes have been documented during a previous study on the behavior of129I in a shallow aquifer near a low-level, radioactive waste management area.Along a 30 cm soil profile at piezometer nest 28 at the Sturgeon Falls study site, the concentrations of129I ranged from approximately 4.3 × 108atoms/g in the uppermost soil litter layer to 5.6 × 107atoms/g in the siltier bottom soil horizons. Over that same profile, stable iodine varied from 4.7 ppm in the upper layers to 3.9 ppm in the lower layers.